It is well known in the art of manufacturing concrete pipe and other similar structures, such as manholes, box sections, catch basins, septic tanks and the like (hereinafter simply "product" or "products"), that a reinforcing wire mesh cage or cages must be provided to produce a product of the required strength. In order to produce a quality concrete product, the reinforcing cage must be positioned so that it will be a predeterimed distance from the inside and outside walls of the finished product. In order to achieve this result, the cage must be properly positioned inside of the space between the forms used to produce the product. The cage cannot, of course, be manufactured to sufficiently close tolerances that it will fit perfectly in the space between the forms at the proper distance from the surfaces of the form walls. More importantly, the cage will be subjected to various forces during the manufacturing process, and it is therefore essential that the cage be properly positioned from the walls of the form and maintained the required distance throughout the casting process. In order to accomplish the proper spacing, there are commonly provided spacing elements which can be fastened to the cage to space it from and maintain it the proper distance from the form walls.
These spacers must also be designed so as to avoid the creation of voids in the finished product, since the product generally must meet specifications that require resistance to hydrostatic pressure. During the casting process, stresses are created on the spacers. When the forms are stripped and while the concrete is still uncured, the forms no longer hold the spacers and these stresses are relieved, allowing the spacers to "pop out". This can create surface bulges and cracks or voids which may produce a hydrostatic leak in the finished product that allows water to enter the structure. Once inside the concrete product, the water will follow leak channels throughout the entire structure because the water will follow the mesh reinforcing cage. Therefore, the structure must be water tight to meet the hydrostatic specifications for such structures, and in order to meet these specifications, it is essential that the spacers resist the forces exerted upon them during the casting process. Hydrostatic problems can also occur if voids are created around the spacers during the casting process. These voids occur if the profile of the spacer does not allow concrete to flow around the spacer.
The two commonly used methods of producing concrete products create different forces on a reinforcing cage and thus upon the spacers used in connection with the cage. In one such method of casting concrete products, an annular space is provided by an inner core and outer jacket which comprise the mold set. The most common procedure is to lower the jacket over the core after the cage is in place. Unless the spacer used is capable of resisting the downward axial forces applied as the jacket is lowered in place, the spacers can be dislodged or distorted.
In another commonly used method of producing concrete products, especially concrete pipe, a packer head rotates inside of an outer cylindrical form so as to pack the concrete through the reinforcing cage and against the wall of the outer form. In this process, the jacket or outer form hinges open and shut, and therefore there is a jacket splice which tends to get out of alignment creating a catch point at the splice. Thus, when this process is used, the spacers for the reinforcing cage must be capable of resisting not only the axial forces that occur, but also the forces upon the spacers as the cage tends to twist during rotation of the packer head. This twisting of the cage can not only dislodge or distort the spacers, but it also drags them along the inside of the jacket and across the jacket splice. The spacers then may tend to catch on the splice or gouge or scar the inner surface of the jacket. There are known a number of different spacers which have been designed in an attempt to resist all of the forces exerted upon the spacers during the casting process, especially those exerted during the packer head process. One such spacer is disclosed in Swenson U.S. Pat. No. 3,471,986, which shows a spacer formed from a flat band of spring steel so as to be provided with an open hook at each end between which is formed the spacing nose. Because of its design, this spacer often will snag on the packer head jacket splice during twisting of the cage. When this happens, the spacer may bend over causing improper spacing, the spacer may become dislodged or the spacer may become bent over and "pop out" when the form is stripped creating a void, or surface crack or bulge. "Pop out" can also occur with this spacer because it can be easily deflected inwardly due to its inherent design using a thin band of steel. Also, because of the solid and relatively large width of the band of this spacer, flow of the concrete during the casting process can be blocked and create voids that lead to hydrostatic leaks. This spacer also tends to gouge the inner wall of the form when the cage twists during the casting process due to the sharp edges of the band.
Another spacer is shown in Schmidgall U.S. Pat. No. 4,301,638 which discloses a spacer formed from a round spring-steel wire into a generally hair pin shape in which there are a pair of parallel legs joined by a closed loop at one end, with the free ends of the legs being formed into hooks. Although spacers of this type are very satisfactory for use in some of the casting processes, when used in the rotating packer head process, the legs tend to bend over or the spacers can become dislodged from the reinforcing cage.
There is therefore a need for an improved spacer useable in any of the casting processes and designed so as to be capable of resisting forces in all directions so that the spacer will not become dislodged, bent or stressed during the casting process resulting in voids or other defects in the finished product. There is a further need for a spacer that will not gouge the inner surfaces of the jacket, and a spacer which has a profile that will allow the concrete to flow completely around the spacer so as to prevent voids that can result in hydrostatic leaks in the finished product. Such an improved spacer should also be of a design that will permit easy and quick installations, preferably without the use of any special tools. Such an improved spacer should also be inexpensive since large quantities are necessarily used during the production of each concrete product.